A variety of theoretical and empirical studies
indicate that the abilities of small-scale experiments
to predict responses to large-scale perturbations vary.
Small-scale experiments often do not predict the directions
of large-scale responses, and relatively few empirical
studies have examined whether small-scale
experiments predict the magnitudes of large-scale
responses. Here we present an empirical example of
small-scale manipulations predicting not only the
directions but also the magnitudes of the eVects of
whole-catchment, decades-long decimation of migratory
freshwater shrimp populations. In streams of
Puerto Rico (USA), we used arena sizes of < 2 m2 in 1-
to 4-week exclosure/enclosure experiments. EVects of
small-scale experiments largely matched those of largescale
shrimp loss above dams for a variety of response
variables (abiotic and biotic factors including epilithic
Wne sediments, algae and organic matter, and invertebrate
grazers, detritivores, and predators). The results
of our extrapolation contrast with studies of small- versus
large-scale perturbations in the temperate zone.
Our Wndings are likely explained by: a set of response
variables that are more dominated by within-patch
processes than exchange processes, an experimental
manipulation that encompassed the characteristic
scales of response variables, our use of open arenas
lacking cage artifacts, and/or our combination of two
distinct experimental approaches (exclosures and
enclosures). Based on our study design, we suggest that
extrapolation across experimental scales can be greatly
enhanced by embedding open arenas within large-scale
conditions that represent all treatment levels.